Various deprecated warnings with WP 6.0.3 and PHP 8.1

[applemango]

I recently tried updating a WP 6.0.3 install to use PHP 8.1 but I immediately get various deprecated warnings from core code.

For example here's a selection:

Deprecated: preg_replace(): Passing null to parameter #3 ($subject) of type array|string is deprecated in /home/applhpqm/public_html/wp-includes/formatting.php on line 5385

Deprecated: trim(): Passing null to parameter #1 ($string) of type string is deprecated in /home/applhpqm/public_html/wp-includes/pluggable.php on line 599

Deprecated: rtrim(): Passing null to parameter #1 ($string) of type string is deprecated in /home/applhpqm/public_html/wp-includes/formatting.php on line 2772

Deprecated: Return type of Requests_Cookie_Jar::offsetExists($key) should either be compatible with ArrayAccess::offsetExists(mixed $offset): bool, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /home/applhpqm/public_html/wp-includes/Requests/Cookie/Jar.php on line 63

Deprecated: Return type of Requests_Utility_CaseInsensitiveDictionary::offsetExists($key) should either be compatible with ArrayAccess::offsetExists(mixed $offset): bool, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /home/applhpqm/public_html/wp-includes/Requests/Utility/CaseInsensitiveDictionary.php on line 40

Deprecated: Return type of Requests_Utility_CaseInsensitiveDictionary::offsetSet($key, $value) should either be compatible with ArrayAccess::offsetSet(mixed $offset, mixed $value): void, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /home/applhpqm/public_html/wp-includes/Requests/Utility/CaseInsensitiveDictionary.php on line 68

Deprecated: http_build_query(): Passing null to parameter #2 ($numeric_prefix) of type string is deprecated in /home/applhpqm/public_html/wp-includes/Requests/Transport/cURL.php on line 345

Downgrading to 8.0 suppresses the errors.

[titsmaker]

Hi, maybe my posting won't add anything to the discussion, I would gladly add it as a comment somewhere in ​https://make.wordpress.org/ but the topic has not been discussed since the very beginning of 2022.
So I would ask WP devs to prioritize these deprecations as many people use

define('WP_DEBUG', true)

even on live sites because testing everything on local machine is often impossible, also that way some edge cases can be revealed. Currently PHP 8.0 is in the very end of it's lifecycle (only security support till November of 2023) and we still can switch to PHP 8.1 as it populate our log with hundreds of such deprecations (mainly in functions.php, formatting.php and different parts of requests library).

[SergeyBiryukov]

Replying to titsmaker:

So I would ask WP devs to prioritize these deprecations

It is worth noting that many of these notices are already resolved in current trunk (6.2-alpha) as part of the work on #54504, #54914, #55656, #55967, #56620, #56681, #56712, and other tickets. I no longer see them on a clean install of 6.2-alpha with PHP 8.2.

[Soean]

@applemango This issue should be fixed in WordPress 6.2, can you confirm it?

[applemango]

@Soean Hey man, I can confirm that the warnings no longer appear! This is awesome and means I can now upgrade my servers to PHP8+. Phew, thank you!